Multi-frequency sensing system and method

Abstract

A sensor system is described with improved measurement accuracy that is achieved by reducing noise, baseline drift, or both based on processing a group of sensor element response signals. The response signals may be received in response to providing stimuli to the sensor element using different excitation frequencies over time. For example, the sensor circuitry may provide excitation signals to the sensing element with multiple excitation frequencies over time. The sensor system may include storage and processing circuitry to receive the response signals and to generate the correction values based on analyzing the received response signals. The sensor system may then provide adjusted response signals by reducing the noise, baseline drift, or both based on the correction values.

What is claimed is: 
     
         1 . A sensor system comprising:
 a sensing element configured to receive a plurality of stimulus signals across a frequency range;   a controller configured to provide one or more control signals to monitor at least one component in a fluid;   an excitation/detection system coupled to the sensing element and the controller, wherein the excitation/detection system is configured to perform one or more operations based on the one or more control signals, wherein the one or more operations comprise:
 providing the plurality of stimulus signals to the sensing element, wherein the excitation/detection system is configured to provide each stimulus signal of the plurality of stimulus signals with a different frequency within the frequency range to the sensing element, wherein the plurality of stimulus signals comprise:
 a first stimulus signal at a first frequency; 
 a second stimulus signal at a second frequency, wherein the second frequency is separated from the first frequency by a first step width; and 
 a third stimulus signal at a third frequency, wherein the third frequency is separated from the second frequency by a second step width; 
 wherein the first stimulus signal, the second stimulus signal, and the third stimulus signal make up at least a portion of a frequency sweep operation across the frequency range, and wherein the first step width and the second step width are based on a type of sensing material of the sensing element, a type of the fluid, or a combination thereof; 
 
 receiving a plurality of sensor responses from the sensing element in response to providing the plurality of stimulus signals; 
 determining one or more noise values, one or more baseline drift values, or both based on analyzing the plurality of sensor responses, wherein analyzing the plurality of sensor responses comprises applying a multivariate curve resolution algorithm configured to reduce the one or more noise values, the one or more baseline drift values, or both; 
 determining at least one noise reduction value, at least one baseline drift reduction value, or both; and 
 reducing at least one noise value of the one or more noise values based on the at least one noise reduction value, at least one baseline drift value of the one or more baseline drift values based on the at least one baseline drift reduction value, or both. 
   
     
     
         2 . The sensor system of  claim 1 , wherein analyzing the plurality of sensor responses comprises applying an analysis of the plurality of stimulus signals with a different frequency within the frequency range to the sensing element over a radio-frequency range of an electromagnetic spectrum. 
     
     
         3 . The sensor system of  claim 1 , wherein the one or more operations comprise analyzing the plurality of sensor responses by applying an additional multivariate curve resolution algorithm. 
     
     
         4 . The sensor system of  claim 1 , wherein the sensor system comprises a first order, a second order, or a higher order sensor. 
     
     
         5 . The sensor system of  claim 1 , wherein the plurality of sensor responses comprises impedance measurements of the sensing element based on providing the plurality of stimulus signals. 
     
     
         6 . The sensor system of  claim 1 , wherein the one or more baseline drift values comprise a drift from a baseline value of a sensor response of the plurality of sensor responses when the sensing element is in contact with a clean carrier gas. 
     
     
         7 . The sensor system of  claim 1 , wherein the one or more noise values comprise fluctuations of the plurality of sensor responses when the sensing element is in contact with a clean carrier gas. 
     
     
         8 . The sensor system of  claim 1 , wherein the sensor system is configured to continuously monitor a concentration of the at least one component in the fluid. 
     
     
         9 . The sensor system of  claim 1 , wherein the sensor system comprises a first order sensor that is configured to utilize a metal oxide-semiconductor (MOS) material that is interrogated with an impedance excitation/detection circuit. 
     
     
         10 . A method, comprising:
 providing, by a controller of a sensor system, one or more control signals to cause generation of a plurality of stimulus signals, each with a different frequency, to a sensing element of the sensor system, wherein the sensing element is configured to receive the plurality of stimulus signals across a frequency range, wherein the plurality of stimulus signals comprise:
 a first stimulus signal at a first frequency; 
 a second stimulus signal at a second frequency, wherein the second frequency is separated from the first frequency by a first step width; and 
 a third stimulus signal at a third frequency, wherein the third frequency is separated from the second frequency by a second step width; 
 wherein the first stimulus signal, the second stimulus signal, and the third stimulus signal make up at least a portion of a frequency sweep operation across the frequency range, and wherein the first step width and the second step width are based on a type of sensing material of the sensing element, a type of fluid, or a combination thereof; 
   receiving, by the controller, a plurality of sensor responses from the sensing element in response to providing the plurality of stimulus signals;   determining, by the controller, one or more noise values, one or more baseline drift values, or both based on analyzing the plurality of sensor responses, wherein analyzing the plurality of sensor responses comprises applying a multivariate curve resolution algorithm configured to reduce the one or more noise values, the one or more baseline drift values, or both;   determining, by the controller, at least one noise reduction value, at least one baseline drift reduction value, or both; and   reducing, by the controller, at least one noise value of the one or more noise values based on the at least one noise reduction value, at least one baseline drift value of the one or more baseline drift values based on the at least one baseline drift reduction value, or both.   
     
     
         11 . The method of  claim 10 , comprising analyzing the plurality of sensor responses by applying an additional multivariate curve resolution algorithm. 
     
     
         12 . The method of  claim 10 , comprising analyzing, by a first order, a second order, or a higher order sensor, the plurality of sensor responses. 
     
     
         13 . The method of  claim 10 , wherein the plurality of sensor responses comprises impedance measured results of the sensing element based on providing the plurality of stimulus signals. 
     
     
         14 . The method of  claim 10 , wherein the one or more baseline drift values comprise a drift from a baseline value of a sensor response of the plurality of sensor responses when the sensing element is in contact with a clean carrier gas and the one or more noise values comprise fluctuations of the plurality of sensor responses when the sensing element is in contact with the clean carrier gas. 
     
     
         15 . A non-transitory computer-readable medium comprising computer-executable instructions that, when executed, are configured to cause a processor to:
 provide one or more control signals to an excitation circuit of a sensor system to generate a plurality of stimulus signals, each with a different frequency, to a sensing element of the sensor system, wherein the sensing element is configured to receive the plurality of stimulus signals across a frequency range, wherein the plurality of stimulus signals comprise:
 a first stimulus signal at a first frequency; 
 a second stimulus signal at a second frequency, wherein the second frequency is separated from the first frequency by a first step width; and 
 a third stimulus signal at a third frequency, wherein the third frequency is separated from the second frequency by a second step width; 
 wherein the first stimulus signal, the second stimulus signal, and the third stimulus signal make up at least a portion of a frequency sweep operation across the frequency range, and wherein the first step width and the second step width are based on a type of sensing material of the sensing element, a type of fluid, or a combination thereof; 
   receive a plurality of sensor responses from the sensing element in response to providing the plurality of stimulus signals;   determine one or more noise values, one or more baseline drift values, or both based on analyzing the plurality of sensor responses, wherein analyzing the plurality of sensor responses comprises applying a multivariate curve resolution algorithm configured to reduce the one or more noise values, the one or more baseline drift values, or both;   determine at least one noise reduction value, at least one baseline drift reduction value, or both; and   reduce at least one noise value of the one or more noise values based on the at least one noise reduction value, at least one baseline drift value of the one or more baseline drift values based on the at least one baseline drift reduction value, or both.   
     
     
         16 . The non-transitory computer-readable medium of  claim 15 , wherein the computer-executable instructions that, when executed, are configured to cause the processor to analyze the plurality of sensor responses by applying an additional multivariate curve resolution algorithm. 
     
     
         17 . The non-transitory computer-readable medium of  claim 15 , wherein the sensor system is a first order, a second order, or a higher order analytical instrument to analyze the plurality of sensor responses. 
     
     
         18 . The non-transitory computer-readable medium of  claim 15 , wherein the plurality of sensor responses comprises impedance measurements of the sensing element based on providing the plurality of stimulus signals. 
     
     
         19 . The non-transitory computer-readable medium of  claim 15 , wherein the one or more baseline drift values comprise a drift from a baseline value of a sensor response of the plurality of sensor responses when the sensing element is in contact with a clean carrier gas and the one or more noise values comprise fluctuations of the plurality of sensor responses when the sensing element is in contact with the clean carrier gas. 
     
     
         20 . The non-transitory computer-readable medium of  claim 15 , wherein the processor is configured to continuously monitor a concentration of at least one component in a fluid.